Spark monitor for fuel burner



July 12, 1966 R. E. SCHRETER ETAL 3,

SPARK MONITOR FOR FUEL BURNER Filed March 11, 1963 FIG.

0 "1 22 INVENTORS 3 ROBERT 4- SCI/R575? AL EXA/VDER J? TURF/Iv MEL 11ml0'. PARKE/E United States Patent 3,261,008 SPARK MONITOR FOR FUEL BURNERRobert E. Schreter, Malverne, Alexander J. Turpin, Stewart Manor, andMelvin LParker, Garden City, N.Y.,

assignors to Hauck Manufacturing Company, Brooklyn,

N.'Y., a corporation of New York Filed Mar. 11, 1963, Ser. No. 264,115

I 11 Claims. (Cl. 340-248) This invention relates to fuel burners havingcontinuous spark gap ignition, and more particularly to a spark monitortherefor.

Large burners using gas are ignited by an igniter producing anelectrical spark. Sometimes a large gas or oil burner has a gas pilotlight, and the pilot light is ignited by a spark. In many industries thespark is run continuously, so'that if the gas pressure fails orfluctuates, there will nevertheless be dependable combustion, and noopportunity for collection of a large amount of unburned fuel withdanger of possible explosion. However, there is no way to be sure thatthe hidden spark gap is actually sparking.

The spark may fail if the electrodes are short circuited, or if carbonbuilds up and fills the gap. The metal at the gap usually is a nickelalloy, and when there is sulphur in the gas being burned, nickelsulphide forms which expands or foams to large dimension, and may shortcircuit the gap. The electrodes may be carelessly handled during aservicing operation and may be bent in such fashion as to close the gap.The electrodes may burn away or be so bent that the gap becomesexcessively large, with resulting failure of the spark.

The primary object of the present invention is to provide a monitorwhich indicates outside the furnace whether thespark is functioning atthe spark gap. A more specific object is to provide a monitor whichincludes a lamp which lights when the spark is operating, and which isextinguished when the spark fails, whether the failure is caused byshort circuiting or open circuiting or severance or disconnection ofeither the high voltage lead or the ground lead to the igniter. Afurther object is to provide such a monitor in which the lamp lightsonly dimly when the spark is weak, and flickers if the spark flickers.Still another object is to provide such a 'device which may be appliedreadily to the exposed outer end of the igniter, and which then receivesthe high voltage lead which usually is connected to the igniter, so thatthe monitor is easily add ed without any change in the existinginstallation.

To accomplish the foregoing general objects, and such other morespecific objects as may hereinafter appear, our invention resides in thespark monitor elements and their relation one to another as arehereinafter more particularly described in the following specification.The specification is accompanied by a drawing in which:

FIG. 1 is a schematic view drawn to small scale and showing an igniterwith a spark monitor applied thereto;

FIG. 2 is a partially sectioned view showing how .the monitor is appliedto the outer end of the igniter;

FIG. 3 is a longitudinal section through a preferred form of monitor;

FIG. 4 is an end view thereof; and

FIG. 5 is a schematic Wiring diagram explanatory of the invention.

Referring to the drawing, and more particularly to FIG. 1, the ignitercomprises a long slender tube 12 made of metal, usually steel. Its outerend may be fitted with a threaded bushing 14 and then is adapted to bescrewed in position somewhat like an enginespark plug, except that theigniter 12 is very much longer. We also use a slip fit bushing insteadof a thread. Its spark gap is indicated at 16, one side being groundedat 18, and the 3,261,008 Patented July 12, 1966 other being connected toa high voltage lead 20. The high voltage supply is usually obtained froma step-up transformer 22, the primary of which usually is energized froman ordinary volt A.C. line 24, but any other conveniently availableprimary voltage may be used. The output voltage of the transformer maybe in the range of 5,000 to 10,000 volts in a typical installation.

Referring now to FIG. 2, the center rod '23 of the igniter isinsulatedly carried by an insulation bushing 25 secured in an outermetal nut 26 by means of a threaded metal bushing 28. The nut 26 has aninternal thread to receive bushing 28, and has an external thread at 14.The center rod 23 terminates in a metal stud or terminal 30 which is soshaped and dimensioned as to receive a spring snap solderless terminal,which terminal is at the free end of the high voltage lead 20 shown inFIG. 1. In the specific form of monitor here shown the monitor has acylindrical case 32 and is applied over the terminal 30. The case 32 ispreferably made of insulation, and itself carries a high voltageterminal 34 which replaces the terminal 30, so that the high voltagelead 20 may be snapped on the upper end of terminal 34 instead of on theterminal 30. Thus the monitor is readily applied to the igniter of anexisting fuel burner.

The lamp is visible through a protective transparent cover or lens 36,which may "be made of glass, or of a transparent plastic material. Themonitor has a metal part 38 which acts as a snap connector or cap whichis received on the terminal 30 of the igniter. The casing 32 may beextended toward the right to provide a protective skirt 39 which helpsimprove the mounting of the monitor on the igniter.

Referring now to FIG. 5, the lamp 40 is a glow discharge lamp having oneor more internal electrodes 42, 44. The glass envelope 46 contains anionizable inert gas indicated by the dot. In the simplest and preferredarrangement the lamp 40 is an ordinary commercially available neon glowlamp having two spaced electrodes 42 and 44, but in the present circuitthese are connected together externally as indicated at 48. The lampalso may be used with only one electrode connected in circuit, and theother electrode free. The reason for this is that the true opposedelectrode is a conductive shield or external electrode 50 disposedaround the lamp. There is a resistor 52 which may be called a lampresistor, connected in series with the internal electrodes 42, 44. Thereis another resistor 54 which may be termed a main resistor, which is inshunt with the series circuit comprising the shield 50, the lamp 40 andthe lamp resistor 52.

The high voltage supply is the transformer 22, the primary of which isenergized from a suitable A.C. source. In this case terminals 24represent an ordinary 110 volt A.C. outlet. One side of the high voltagesecondary is grounded, as shown at 56, and the other side is connectedto the high voltage lead 20, which ordinarily would be applied directlyto the terminal 30 of the igniter 12. The other side of spark gap 16 isgrounded as indicated at 18. It will be evident from inspection of FIG.5 that the monitor is connected electrically in series with the highvoltage supply to the igniter.

In a typical and preferred case the lamp 40 is a type NESlI-I neon lamp;the lamp resistor 52 is a /2 watt resistor having a value of 2500 ohms;and the main resistor 54 is a two watt resistor having a value of 3900ohms. The transformer output voltage is 6000 volts. The spark gap was0.046 inch in length, this being a standard gap already in use. However,all these values are subject to very wide variation, as is discussedlater in greater detail.

The structural arrangement of one form of monitor is illustrated inFIGS. 3 and 4 of the drawing. The casing 32 is cylindrical and made ofan insulating material. One end of the lamp is shown at 40, the lampbeing surrounded by a cylindrical metal shield 50. The latter is carriedby one end of an arm 60, the other end of which is secured to the innerend of the high voltage terminal 34.

The lamp is received in a socket 62 carried in an insulation tube 64,and the parts 62, 64 are carried by a bracket 66. The lamp has twoelectrodes and two leads, both of which are preferably connected to thelamp resistor 52, one connection being shown at 68. The main resistor 54has one lead 70 connected to the high voltage terminal 34, or morespecifically to the bracket 66. The other lead 72 of resistor 54, andthe other lead 74 of resistor 52, are connected in common to the stud 76of a spring cap 38. This is carried by an insulation disc or plug 78which is secured in cylinder 32 by means of a plurality of screws 80.For a reason previously explained, the cap 38 is preferably locateddeeply within the housing 32.

The spring cap may assume a number of known forms. In the present caseit comprises a fixed hollow cylinder 38 around which there is applied aspring clip 82 having parts received through slots in the cylinder wall,and adapted to engage an undercut in the terminal 30 (FIG. 2) of theigniter with a snap fit. The lens 36 may be threaded and screwed on to amating thread formed at the end of casing 32, as shown at 84.

As previously mentioned, the device is operable despite wide variationin the component values employed. The usual two-electrode neon lamp willfunction with only one electrode connected, but it is found that if thetwo electrodes are joined, a glow appears around each electrode, thusincreasing the light produced, and we therefore prefer to employ bothelectrodes. A special lamp could be constructed with a single electrode,or with three or more electrodes, and all should prove operable.

As examples of the invention which we have made, we have used a typeNE48 lamp with a lamp resistor of 3900 ohms. The main resistor variedfrom 2400 ohms, with good light intensity, up to a value of ten millionohms, at which time the light intensity was reduced to only a fair topoor value.

We have used an NE48 neon lamp with a lamp resistor of 900 ohms, andwith a main resistor varying from 100,- 000 ohms up to ten million ohms.In that case the light intensity was still good at ten million ohms. Itwas also good at 100,000 ohms, but becoming poorer at any lower value.

We have used a type NES 1H neon lamp with a lamp resistor of 3900 ohms,and with a main resistor of from 230 to 1000 ohms. The light intensitywas very good at 230 ohms, and was less but still good at 1000 ohms. Forthe present purpose we prefer a good rather than very good lightintensity, but only for thereason that the life of the lamp is reducedwhen operated at very high intensity, and itis preferred to give theequipment long life before requiring lamp replacement. Even then thespark monitor is fail safe in that if the lamp fails it will go out,which serves as a warning.

We have used the same lamp type NESlH with a lamp resistor of 10,000ohms and with a main resistor ranging from 15 ohms upward to 3,000 ohms.In this case the light intensity was very good at the low value, but thehigher 'value would be preferred for long life. At values above 3,000ohms the light intensity tends to fall off.

We have used the same lamp with a lamp resistor of 5,000 ohms, and witha main resistor ranging from 15 to 1500 ohms. Here again, the lightintensity was very good (and therefore excessive, as explained above) at15 ohms. It was good at 1500 ohms, but fell off at values higher than1500 ohms.

We have used the same lamp with a lamp resistor of 900 ohms, and with amain resistor varying from 100 to 680 ohms. The light intensity wasfound to be good throughout that range, but with a tendency to fall oilor become poor above 680 ohms.

In all cases in which the lamp was specified to be NESIH, anothersimilar lamp designated NESl may be used, but with a slight reduction inlight intensity.

In all cases the current carrying capacity of the main resistor 54 ispreferably greater than that of the lamp resister 52. The latter carriesonly the negligible current needed to operate the glow lamp.

We are not certain of the theory of operation of the spark monitor, andit may be considered to be an empirical discovery. One theory is thatwhen using an internal and an external electrode, a very high firingvoltage is required. When the spark gap is short circuited the secondaryvoltage presumably drops below the firing voltage and the lamp then doesnot glow. Inasmuch as we are uncertain of the theory of operation, we donot wish the patent to be bound by this suggested theory. It issuificient to say that in operation the neon lamp glows as long as aspark is present at the spark gap, and that if the spark gap is shortcircuited the neon lamp is extinguished. An open circuit alsoextinguishes the lamp.

The NES 1H lamp is preferred because it is small and compact and has ahigh intensity glow. However, we have conducted successful operationwith not only that lamp and the NE51 and NE48 previously mentioned, butalso the NE16 and the NE30, but then the size of the metal shield orexternal electrode has to be changed, and also the resistance values.

In general the resistance values are dependent on a number of factors,including the length and diameter of the external electrode. An increasein diameter reduces the intensity of the glow. An increase in lengthincreases the glow up to a point, following which an exaggerated lengthreduces the glow.

It should be mentioned that the main resistor serves an additionalpurpose in acting as a suppressor which reduces oscillation in thecircuit, and this in turn prolongs the igniter life at the spark gap.For suppression purposes the main resistor is preferably kept between2,000 and 20,000 ohms.

Decreasing the resistive value of the lamp resistor tends to increasethe brightness of the lamp, if other things are held constant.

The lamp connection employed is of course unusual in that the twointernal electrodes are tied together, and the glass envelope of thelamp is used as a dielectric between the internal electrodes and theexternal electrode or shield.

It is believed that the construction, method of use, and operation ofour improved spark monitor, as well as the advantages therof, will beapparent from the foregoing detailed description. It will also beapparent that while we have shown and described the invention in severalpreferred forms, changes may be made in the structure and in thecomponent values shown, without departing from the scope of theinvention as sought to be defined in the following claims.

We claim:

1. A spark monitor for a large fuel burner for use in industrialfurnaces or the like, said burner lbeing ignited by a spark gap igniterenergized by a high voltage supply, said igniter having a high voltageterminal, said high voltage supply terminating in a spring terminal capdimensioned to fit on the high voltage terminal voltage supply line, aconnection from said terminal to one end of the shunt circuit, and aconnection from said spring cap to the other end of the shunt circuit,whereby high voltage supply to the igniter.

2. A spark monitor as defined in claim 1 in which the lamp is a typeNE48, and in which the lamp resistor has a value of from 900 to 3900ohms, and in which the main resistor has a value of from 2400 to millionohms.

3. A spark monitor as defined in claim 1 in which the lamp is a typeNE48, and in which the lamp resistor has the monitor is connectedelectrically in series with the a value of 3900 ohms, and in which themain resistor has a value of from 2400 to 10 million ohms.

4. A spark monitor as defined in claim 1 in which the lamp is a typeNE48, and in which the lamp resistor has a value of 3900 ohms, and inwhich the main resistor has a value of from 100,00 to 1 million ohms.

5. A spark monitor as defined in claim 1 in which the lamp is a typeNE51H, and in which the lamp resistor has a value of 3900 ohms, and inwhich the main resistor has a value of from 330 to 1000 ohms.

6. A spark monitor as defined in claim 1 in which the lamp is a typeNESIH, and in which the lamp resistor has a value of 10,000 ohms, and inwhich the main resistor has a value of from to 3000 ohms.

7. A spark monitor as defined in claim 1 in which the lamp is a type NE51H, and in which the lamp resistor has a value of 5000 ohms, and inwhich the main resistor has a value of from 15 to 1500 ohms.

8. A spark monitor as defined in claim 1 in which the lamp is a typeNESlH, and in which the lamp resistor has a value of 900 ohms, and inwhich the main resistor has a value of from 100 to 680 ohms.

9. A spark monitor as defined in claim 1 in which the lamp is a typeNE51H, and in which the lamp resistor has a value of from 900 ohms to10,000 ohms, and in which the main resistor has a value of from 15 to3000 ohms.

10. A spark monitor for a large fuel burner for use in industrialfurnaces or the like, said burner being ignited by a spark gap igniterenergized by a high voltage supply, said igniter having a high voltageterminal, said high voltage supply terminating in a spring terminal capdimensioned to fit on the high voltage terminal of the igniter, saidmonitor comprising a neon glow lamp having two internal electrodes withleads connected thereto, means joining the leads of said electrodesoutside the lamp, a conductive cylindrical shield fitting closely aroundthe lamp and acting as an external electrode, a lamp resistor in serieswith the joined leads of both internal lamp electrodes, a main resistorin shunt with a series circuit which series circuit comprises theshield, the lamp, and the lamp resistor, a cylindrical insulationhousing for the aforesaid parts, said housing exposing the lamp at oneend, the other end having .a deeply recessed spring cap dimensioned tosnap on the high voltage terminal of the igniter, the body of saidhousing having a high voltage terminal shaped like that of the igniterto receive the spring terminal cap of the high voltage supply line, aconnection from said terminal to one end of the shunt circuit, and aconnection from said spring cap to the other end of the shunt circuit,whereby the monitor is connected electrically in series with the highvoltage supply to the igniter.

11. A spark monitor for a large fuel burner for use in industrialfurnaces or the like, said burner being ignited by a spark gap igniterenergized by a high voltage supply, said monitor comprising a neon glowlamp having the usual two internal electrodes with leads connectedthereto, means joining the lead of said electrodes outside the lamp, aconductive cylindrical shield fitting closely around the lamp andactingas anexternal electrode, a lamp resistor in series with the joinedleads of both internal lamp electrodes, and a main resistor in shuntwith a series circuit which series circuit comprises the shield, thelamp, and the lamp resistor, said monitor being connected electricallyin series with the high voltage supply to the igniter.

References Cited by the Examiner UNITED STATES PATENTS 1,907,069 5/1933Heaton 3115-132X 1,931,225 10/1933 Heaton 340-253X 2,004,587 6/1935Schroter 313-201 X 2,006,341 7/1935 Berg et al 32417 X 2,068,147 1/1937Miller 315-137 X 2,482,016 9/1949 McCoy 324-17 X 2,765,426 10/1956Faulkner 315-X 2,970,303 1/1961 Williams 340-252X 3,095,557 6/1963 Bryan340-248 3,099,828 7/1963 Kelley 340-248 NEIL C. READ, Primary Examiner.D. K. MYER, Assistant Examiner.

1. A SPARK MONITOR FOR A LARGE FUEL BURNER FOR USE IN INDUSTRIALFURNACES OR THE LIKE, SAID BURNER BEING IGNITED BY A SPARK GAP IGNITERENERGIZED BY A HIGH VOLTAGE SUPPLY, SAID IGNITER HAVING A HIGH VOLTAGETERMINAL, SAID HIGH VOLTAGES SUPPLY TERMINATING IN A SPRING TERMINAL CAPDIMENSIONED TO FIT ON THE HIGH VOLTAGE TERMINAL OF THE IGNITER, SAIDMONITOR COMPRISING A NEON GLOW LAMP HAVING AN INTERNAL ELECTRODE WITH ALEAD CONNECTED THERETO, A CONDUCTIVE SHIELD ADJACENT THE LAMP AND ACTINGAS AN EXTERNAL ELECTRODE, A LAMP RESISTOR IN SERIES WITH SAID LEAD OFSAID INTERNAL LAMP ELECTRODE, A MAIN RESISTOR IN SHUNT WITH A SERIESCIRCUIT WHICH SERIES CIRCUIT COMPRISES THE SHIELD, THE LAMP, AND THELAMP RESISTOR, A HOUSING FOR THE AFORESAID PARTS, SAID HOUSING EXPOSINGTHE LAMP AT ONE END, THE OTHER END HAVING A SPRING CAP DIMENSIONED TOSNAP ON THE HIGH VOLTAGE TERMINAL OF THE IGNITER, THE BODY OF SAIDHOUSING HAVING A HIGH VOLTAGE TERMINAL SHAPED LIKE THAT OF THE IGNITERTO RECEIVE THE SPRING TERMINAL CAP TO THE HIGH VOLTAGE SUPPLY LINE, ACONNECTION FROM SAID TERMINAL TO ONE END OF THE SHUNT CIRCUIT, AND ACONNECTION FROM SAID SPRING CAP TO THE OTHER END OF THE SHUNT CIRCUIT,WHEREBY HIGH VOLTAGE SUPPLY TO THE IGNITER.